| Title |
Effect of Annealing Temperature on Microstructure and Properties of the Pressureless-Sintered SiC-ZrB_2 Electroconductive Ceramic Composites |
| Authors |
신용덕(Shin, Yong-Deok) ; 주진영(Ju, Jin-Young) |
| Keywords |
Annealing Temperature ; Electroconductive Ceramic Composites ; Pressureless-Sintered ; Pauw Method ; PTCR In Situ YAG(Al_5Y_3O_{12}) |
| Abstract |
The effect of pressureless-sintered temperature on the densification behavior, mechanical and electrical properties of the SiC-ZrB_2 electroconductive ceramic composites was investigated. The SiC-ZrB_2 electroconductive ceramic composites were pressureless-sintered for 2 hours at temperatures in the range of 1,750~1,900[°C], with an addition of 12[wt%] of Al_2O_3+Y_2O_3(6:4 mixture of Al_2O_3 and Y_2O_3) as a sintering aid. The relative density and mechanical properties are increased markedly at temperatures in the range of 1,850~1,900[{°}C]. The relative density, flexural strength, vicker's hardness and fracture toughness showed the highest value of 81.1[%], 230[MPa], 9.88[GPa] and 6.05[MPa m^{1/2}] for SiC-ZrB_2 composites of 1,900[{°}C] sintering temperature at room temperature respectively. The electrical resistivity was measured by the Pauw method in the temperature ranges from 25[{°}C] to 700[{°}C], The electrical resistivity showed the value of 1.36×10^{-4}, 3.83×10^{-4}, 3.51×10^{-4} and 3.2×10^{-4}[{Ω}·cm] for SZ1750, SZ1800, SZ1850 and SZ1900 respectively at room temperature. The electrical resistivity of the composites was all PTCR(Positive Temperature Coefficient Resistivity). The resistance temperature coefficient showed the value of 4.194×10^{-3}, 3,740×10^{-3}, 2,993×10^{-3}, 3,472×10^{-3}/[°C} for SZ1750, SZ1800, SZ1850 and SZ1900 respectively in the temperature ranges from 25[°C] to 700[°C], It is assumed that because polycrystallines such as recrystallized SiC-ZrB_2 electroconductive ceramic composites, contain of porosity and In Situ YAG(Al_5Y_3O_{12}) crystal grain boundaries, their electrical conduction mechanism are complicated. In addition, because the condition of such grain boundaries due to Al_2O_3+Y_2O_3 additives widely varies with sintering temperature, electrical resistivity of the SiC-ZrB_2 electroconductive ceramic composites with sintering temperature also varies with sintering condition. It is convinced that {β}-SiC based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering. |